1. Field of Invention
The invention relates to an image forming apparatus with a charging device, an image holding member, and a developing device arranged substantially in a line, and a process cartridge.
2. Description of Related Art
In conventional image forming apparatuses such as laser printers and copiers, a surface of a photosensitive drum, which is made by laminating a carrier generation layer and a carrier transport layer on a base layer, is charged with a corona discharge by a charger. The photosensitive drum is irradiated with a laser beam emitted from a scanner unit and an electrostatic latent image is formed on the photosensitive drum. The latent image is developed using a developing agent such as toner carried on a developing roller, transferred to a recording medium such as paper by a transfer roller, and heated and transferred entirely to the recording medium by a fixing device. In this way, images are formed on the recording medium.
In the image forming apparatus structured above, to realize the above described image formation process, the charger, the developing roller, and the transfer roller are disposed in this order along a circumference of the photosensitive drum upstream from a direction of rotation of the photosensitive drum. The photosensitive drum is structured to receive a laser beam from the scanner unit between the charger and the developing roller. Thus, there are a lot of parts to be placed around the photosensitive drum. In Japanese Laid-Open Patent Publication No. 2000-250378, the charger is disposed at an upper portion of the photosensitive drum. A portion of the photosensitive drum that is irradiated with a laser beam emitted from the scanner unit is provided immediately downstream from the upper portion of the photosensitive drum, the developing roller is disposed to a side of the photosensitive drum further downstream from the portion, and the transfer roller is disposed at a lower portion of the photosensitive drum. Thus, wasted space around the photosensitive drum is reduced and parts are arranged efficiently.